Agriculture Reference
In-Depth Information
MACROPROPAGATION
Grafting is the most efficient way to rapidly effect
improvements in these fruit trees:
Adansonia digitata
(85-100% graft success),
Mangifera indica
(97%),
Uapaca kirkiana
(80%),
Strychnos cocculoides
(40-79%),
Sclerocarya birrea
(52-80%),
Vangueria infausta
, (100%) and
Parinari curatellifolia
(71%) (Mhango and Akinnifesi, 2001) compared
favourably with exotics such as mango (90%) in the same trial. Air-layers were
promising for
Uapaca kirkiana
(63%) but were not successful for
Parinari
and
Strychnos
species (Mhango and Akinnifesi, 2001). Interestingly, rooting
hormone did not improve the rooting of
Uapaca
air-layers. Both grafting and
air-layering set during November-December gave the best results. Top-wedge
and whip methods were the most successful for grafting. The results showed that
the factors determining grafting success are the skill of the person, the time of
the year the scion is collected and the interval between scion collection and
grafting (Akinnifesi
et al
., 2004a, 2006).
MICROPROPAGATION
As the awareness of the potential of indigenous fruit trees
increases, demand will inevitably increase, and, considering the massive tree-
planting initiatives in the many countries in the miombo ecoregion, explosive
demands for high-value trees, including indigenous fruit trees, cannot be
accommodated in the short run. All known approaches of vegetative propagation
are inherently slow and are attractive for only a few thousand farmers. For
instance, to produce rootstocks for grafting
Uapaca kirkiana
, at least 1 year of
seedling growth is required. In order to be able to deliver high-quality propagules
of superior indigenous fruits in sufficient quantities for wider adoption, it is
important to explore biotechnological methods, such as tissue culture. Currently,
research on tissue culture has been conducted in the ICRAF programme in
southern Africa on some priority indigenous fruit trees, especially
Uapaca
kirkiana
,
U. nitida
and
Pappea capensis
(plum), with the objective of developing
a reproducible clonal protocol for rapid regeneration and multiplication, and to
determine early graft compatibility using
in vitro
techniques (Mng'omba, 2007).
Incompatibility between stock and scion in the fruit orchard could constitute a
major bottleneck to production. Simons (1987) estimated that half a million
grafted peach trees had died in the southeast of the USA as a result of scion/stock
incompatibility. Selection of scion and stock for compatibility is important for
profitable orchard establishment and management.
Phenolic compounds and
p
-cumaric acids have been implicated in early
graft incompatibility in
Uapaca kirkiana
. Plants normally release phenolics to
heal wounds and as a defensive mechanism against pathogen attack,
lignification and protein biding. Multiplication was much easier in
P. capensis
than in
Uapaca kirkiana
. Preconditioning grafted
Uapaca kirkiana
trees and
decontaminating explants in 0.1% mercuric chloride for 8 min was found to be
effective in achieving a high level of
in vitro
culture asepsis in
Uapaca kirkiana
.
In vitro
propagation of
Uapaca kirkiana
is feasible with sprouts excised from the
preconditioned trees (Mng'omba, 2007). Shoot multiplication was effective
using
1
/
2
strength Murashige and Skoog (MS) medium plus 2.5 mg/l of IBA
(indole butyric acid) medium. Results will be improved by micropropagating
Uapaca kirkiana
in such a way that stock plants are not stressed and ensuring
Search WWH ::
Custom Search